T'S liix 




im 



CITY OF NEW YORK 
BOARD OF ESTIMATE AND APPORTIONMENT 

STANDARD METHODS 

OF TESTING 
RUBBER MATERIALS 




JULY ilSMi 1917 



ISSUED BY 



THE BUREAU OF CONTRACT SUPERVISION 

A 

ROOM 1327 MUNICIPAL BUILDING 



j.^^pas". 



D. of D. 
SEP 18 I9U 






PHYSICAL 

GENEEAL. 

The contracting department shall select and take all samples for testing. 
The number of samples and the quantity to be taken from the deliveries 
will depend upon the size of the articles and the quantity delivered. 

Upon request from the testing laboratory the contracting department 
shall furnish any additional samples required. 

Samples shall fairly represent the delivery and pieces shall be taken 
from not less than 1% of the number of imits delivered. 

The results of tensile strength, elongation and set tests, as reported, shall Averages 
be the average obtained from the samples received by the laboratory. Not 
less than 3 test pieces from each sample shall be tested and their results 
taken in calculating the average unless some individual result is apparently 
in error, in which case a retest shall be made. 

Physical tests of rubber shall be made with the temperature of the air -^mpetaum ot 
not lower than 65° or higher than 90° F., and the test specimens shall be ° *'°°°'' 
at rest in this temperature for not less than 30 minutes before testing. 

All measurements of time shall be taken with stop watch accurate to 0.2 Time, 
second. 

PEEPAEATION OF TEST PIECES. 

Tests pieces of rubber shall be stamped out with a die, whenever prac- General, 
ticable to do so. 

Test pieces of rubber for tensile strength, elongation and set tests J^^^f^^^'^'^Mt 
shall be cut out with a die either of the constricted bar or ring type. The test pieces, 
same test piece shall be used for making all three tests. When the bar 
test piece is prepared a die shall be used that will make the constricted 
part 14 iiich in width. 

All pieces for these tests shall have the backing entirely removed and 
any corrugations or irregularities of any kind shall be accurately buffed off 
to make a uniform smooth surface, except the pieces that are to be used 
for testing the strength across the seam which shall not be buffed. 

Test pieces which have become burnt in buffing shall be discarded. 

Test pieces of rubber valves, odd shaped rubber articles, et cetera, 
shall, whenever possible, be cut down on a lathe to an even thickness of 
not more than Ys inch and then cut out to shape for testing with a die. 

If it is necessary to use naphtha to remove the backing or to separate 
the rubber from the plies, the naphtha shall be what is technically known 
as 76° Baum6, free from oil. 



li ' 5 w 



•pnnod B JO x-q o:^ o^bhiodb si qoiqAi. 
sii^BiBdclB m uo apBin aq n^qs s:^s^| ^^Tla^s aiisna^ nv .■sra?»J»id7 

:sM.onoj SB apBTH 
aq HBqs pimodnioo jeqqru eq^ jo q^nai^s 9itsn8| jo ^OI^B^T^IJ^:^^p aqx 

•SNOi>LVJs[iHaai-aa 

•a^qissod laAauaq^ gnoi saqoui gx iiBq:^ ssai %oti :^TlD aq 
HBqs '•D:^^ 'Sni^pq '^^a^tSBS ' 'Sni5[0Bd sb qons ivue^vm foif /o saosii 227 

•saqoni S/1;X ^noqB loj 
paiiBis sand 044 aq:j jo no^BiBdas b pnB 'send OAi^ ;iiq n^ o^ ^op psddF^s 
aq n^qs pnB apm qoui x' ^^o Ip^BiTiooB aq n^qs saaart^ ?S9? 6Mi?28ff 

•saqDtn 
ZAX poqB joj pa^iB^s aq n^^s jaqqiu puB Sui^aaqs naaM:^3q noi:^BiBdas y 
•apiA saqoni S/xI ^^m^ P dii:ts b no apm qoni x Sni^aaqs jo dl^s v gniABai 
a;isoddo ^i^oBxa paiBdaid aq Tl^qs aoaid :jsa^ 9q:^ 'Jioiq:t qom s/t ^^q^ ^•lo™ 
si'^Bd laqqni aq; ji ^Bq; :;daoxa 'asoq pami jaqqnj no;; 00 loj sb januBin 
axuBS aq; ui paiBdaad aq HBqs ssoaid ?sa? Buiopvd xdqqnj, ■pd}pvq ouqv^ 

•{aipuBui aq; loj 
;no pa^up a-ioo b aABq HBqs sdpj^v Miiiwis puv Bmopvd punoj, pyps 

•aq jCbui asBO aq; sb 'sjjooq 10 
sduiBp JO Snraa;sBj ladoid ;iniiad 0; ;nB;sTp qStiona ibj pnB aoaid aq; jo 
q;pm n^J p9JJB;s aq n^^qs apBin aq 0; ;sa; aq; q;ui aonBpioooB m sja^fBi aq; 
iiaaiii;aq jo oiiqBj aq; pnB laqqni aq; uaam;aq Tioi;BiBdas y -papnBia 0; no 
gnipip ;iiniad 0; jb^oiio ;jai pnB 'apm qoni x XpsiaASUBi; ;tid ;tp;BiiioDB aq 
^^Bqs sapi;iB iBpniis puB Bmopvd punou. 'dsoii pdddvxm /o sdOdid ■^sdj, 

•saqont %x ^noqB joj pa;iB;s aq n^qs dij;;s siq; 
JO laAOo poB Sninij naaAi;aq noi;BiBdas y -apm saqoni %! -i^aoo jo dii;s 
■B no paqiii;sipnii apm qoni x ^nrai^ laqqru jo dij;s b SniABa^ 'ouqBj 
aq; SnunCni ;iioq;iM. 'apis qoBa no j;o paniinti; XjUBap pnB jfunjaiBO aq 
•[^Bqs g'niiiii jaqqni aq; jo qoni J^ "aoaid aq; jo q;Sna| \\r^^ aq; ;Bg ;no 
piB^ aq nBO yfaq; ;Bq; os s^bai aq; qgnoiq; ;no aq ijBqs Xaqj^ -aonaiaj 
-nmoip aq; jo q;Sna^ ipij pnB apm saqoni %x jfpsiaAsnBi; ;no ^p;bitioob aq 
X^Bqs S903yl jsa? asoi/ pdpwj,q puv sdond i-Sdj. dsoii pami Mqqru uof^oQ 

■sd\xii asaq; q;m aonBpioooB ni niaq; aiBdaid o; a^qBOT;oBidnii st ;i jt 
'noi;B05pads ;inn aq; ni loj pa^^BO sb jannBin aq; ni paiBdaid aq ]|Bqs sapi';j;B 
padsqs ppo iaq;o pnB s'p^svS pdpiom 'Sdinjudl 'SMt[Svm wo// sdoaid jsaj; 

•noi;oajip jCnB ni ;no aq jCbiu imj,9ivm p^srsB j.o duxopvd 'Bmjisg; 

•^n^nipn;iSnoj ;no aq n^qs saoaid ;sa; aq; asBO qoiqAi ni 'naj[B; aq ;onnBD 
;naniainsBain ^Bai;DBid b ;Bq; j^Bnis os si ia;aniBip aq; ssapin jfpsiaAsnBi; 
;tio aq n^qs sapi;jB xB^raiis pnB Smipvd punou, 'dsoii /o spuy>[ ny 

: SAiojpj 
SB paiBdajd pnB ;no aq ^Bqs s;sa; noisaqpB 10 notjouj joj saoatd ;sax 

•Sngjnq ni 
;nmq aniooaq 0; aoaid ;sa; aq; Aio^B 0; ;on nai[B; aq jpqs aiBO ;Bai£) 

•Sni;sa; aiojaq sa;nnitu ox ^^q^ ssa^ ;on joj ;sai ;b niBinai n^q^ 
saoaid ;sa; aq; 'anop Snignq pnB paAoniai si §ni5[0Bq aiaqAv sasBo \\^ nj 

•Sni;sa; aiojaq inoq x tiBq; ssa^ ;on joj ;saj ;b 
trxBinai 0; paiionB aq n^qs saoaid ;sa; aq; pasn naaq SBq Bq;qdBn naq^ 



saooid %en noi^otjj 



Grips: When bar test pieces are used, the grips for holding the test 
pieces shall be such that they will tighten automatically. 

Ring test pieces shall be placed over the revolving rollers or pins pro- 
vided for them. 

Marking the bar test piece: The bar test pieces shall be stamped in the 
center portion with two lines 2 inches apart, using an ink pad stamp. The 
distance between the outside edges of these stamped lines shall be accurate 
to 0.01 inch, and the width of the stamped line shall not be more than 
0.01 inch. 

Measurement of bar test piece: The width and thickness of the test 
pieces shall be accurately determined at three points equidistant between 
the marks. Measurements shall be accurate to the nearest thousandth 
inch. 

Measurement of ring test piece: The width and thickness of the test 
ring shall be accurately determined at not less than four opposite points 
on the ring, care being taken to get the minimum cross section as near as 
possible, the area of which shall be used in computing the tensile strength. 
Measurements shall be accurate to the nearest thousandth inch. 

Breaking: Bar test pieces shall be tightly fastened in the jaws and 
brought just taut. The machine shall then be started and the speed so 
regulated throughout the entire test, that the jaws separate at the uniform 
rate of 20 inches per minute. 

The number of pounds necessary to break the test piece shall be read 
off to the nearest 0.1 of a pound and computed to pounds per square inch, 
using the measui-ements nearest to the break. 

When breaking the ring test piece the ring shall be slipped over the 
revolving bearings provided for it and the procedure continued exactly as 
for the bar test piece, the speed being so regulated that it will give an 
equivalent elongation of test piece per minute. 

Bar and ring test pieces shall be prepared as described under the caption °^^'^°n^™ °' 
Preparation of Test Pieces, except that no buffing shall be done. ^''*" 

In cutting, the seam shall be centered in the middle of the bar test 
piece, at right angles to the axis, as nearly as possible. 

The center of the seam shall be made to lie along the diameter of the 
ring test piece as nearly as possible. 

The number of pounds necessary to break the test piece shall be read 
off to the nearest 0.1 pound and computed to pounds per linear inch of 
seam. 

The elongation at the breaking point shall be accurately determined Determinationsof 
during the tensile strength test as follows : breaSngpoint. * 

On the bar test a rule graduated to tenths of an inch shall be kept 
opposite the two marks and the distance the outside edges of these two 
marks are apart at the instant of breaking shall be noted. 

This distance shall be computed into per cent of elongation, i. e., if 
the marks are 3 inches apart at the start and 12 inches apart at the break, that 
piece would have a 500 per cent elongation. 

-lo 2 

X 100 = 500 per cent. 



•pipuCTa B JO pB9:jsni diUBjo b q:^m pBsq ja^od eij; 04 pana^suj aq n^s^s sssaij 
}S9j, /o uoi}mvdd.ij JO noi^fd^D eq:j japnn paquosap sb paiBdaad sb aoaid :^S9:^ 
Qv\} JO DuqBj 9q; pq| :jd9o'x9 'sdOdij jsaj; miuomq puv ssojj Udqqnn uoi:^dBD 
9q; lapnn Suiogaioj aq:} ni p9qiiDS9id sb %obx9 pa^sa:^ aq \\^^b jajoBiBqo 
jByiniis B JO saoatd :}sa^ puB sao'aid :^sa^ asoq aig pautx jaqqtu no;:^OQ 

•paijBJBdas aq n^^s sia^B^ jo laXBj uoi^ouj aitjna aqj;, 

•aaiAap Suipiooaj ot;Brao:jTiB ub ho papjooai aq R.'sm pBOj siqx 

•pa:;BiBdas q:jSu9i ^b^o; aq; jo o^q uBq:^ \\-^-aa\ 
p;o:} i9;b9iS b joj ;u9ra9jmbai uoi:^BOijioads aq:> Aiopq n^J ■Jon saop |i :^Bq; 
©as o:^ paqD:^BAi I^^ubjshod aq ^Bqs pBoj aq; saonauinioo uoi^BiBdas la^jy 

•(pBaq j9Avod aq; jo pagds) a;miira jad saqoni oai; jo ajBj 
niiojitm aq; ;b uni antqoBni aq; puB pasiBi aq n^qs saqo;np ;qStaA\ aqj, 

•pjpnBni 9q; jbao paa9;nao pnB gui;siAi; ;noq;m auiqDBUi §ui;sa; aq; jo 
pBaq Snipjooai aq; o; pgdraBp aq n^^s 909id ;s9; aq; jo pna aaij aqj^ 

•pB9q laiiod aq; 0; paqoB;;B 
irid B o; no paddip aq n^qs 8o«ld ni aoaid ;sa; aq; q;;* ]aipuBra aqj, 

•naxnioads aq; jo aptsni aq; sb ja;9raBip 
araBS aq; jo puB aaaid ;sa; aq; uBq; iapu\ qoni % ]8jpnBui b 0; no paddies aq 
y[Bqs saoaid ;sa; jb^diio paddBiJii j9q;o pnB asoq jaqqru \\y :9unp990j.^ 

•9niqoBni §ni;sa; a^isna; 
■B no apBin aq ^'^qs s;s3; q;Saai;s uoisaqpB 10 uoi;oiij hy :snivj.vddy 

: SAO^oj SB apBui aq ijBqs oiiqBj jo sia^^B^ aq; n99m;9q 10 ouqBj aq; puB 
laqqni 9q; n99M;aq q;3iiai;s notsaqpB jo not;Duj jo uoi;Bnnnia;ap aqj, 

■siaq;o j£q paoBfdaj aq j^Bqs saoatd ;s9; aq; s^iBy 
JO Tioi;BAj:9sqo aq; nuguoo s;s9; gq; jo s;p\saj aq; ji pnB 'sjoajap 10 SAiBg 
JOJ pa'nnnBxa aq n^qs sSnij ;s9; pnB sjBq ;sa; q;oq jo saoBjins najjojq aqj^ 

•apBni ;sa; jaq;onB pnB 'noi;Buinija;ap 
inB JOJ aAi;oajap sb pajapisnoo aq ^jBqs n9niio9ds 9q; ';s9; q;Sn9j;s a^isna; aq; 
Snunp aoaid ;sa; jBq aq; no sjfJBni 9SbS gq; apis;no sjnooo ijBajq aq; jj 

•;naD jad x'O ;sajB9n gq; 0; papjooa.i 
;piS9J aq; pnB 'ain;dui ;b noi;BSnop jo ;naD jad aq; Xq papuip ';nao jad jpq 
;sajBan aq; 0; j;o pBai si (;as |Bn;oB) q;Snai ni asBaioni aqj^ -Suu jBntSiio 
aq; jo ja;aniBip apisni aq; sb j9;araBip aiuBS aq; jo ostp pi^os b pnnoiB 
pgjnsBani A^pijajBO aonajajuiuoip janax aq; aABq jjBqs saoajd ;sa; Snijj 

•;nao jad X'O ;saJBgn aq; 0; ain;dni ;b noi;Bgnoia aq; jo 
aSB;naDjad 0; pa;ndiuoD gq \\v\\s pnB ';as iBn;DB aq; si saqoni g snnini s;n9inajn 
-SBam om; asaq; jo niiis aqj^ •noi;jod jgq;o aq; no ;niod najjojq ;sajBan Snt 
-pnodsajjoo aq; raojj jannBin auiBS aq; ni puB 'qoni XO'O ;saJBan aq; 0; noi;jo(i 
ngj[Ojq gno no sixb aq; gnojB ^[pjgjBO pajnsBani ;niod na^^ojq ;saq;jnj aq; 
o; anil ^^^ P 9pis;no aq; niojj aanBjsip aq; aABq ^^qs saogid ;sa; jBg 

•qo;BAV do;s b q;m naj{B; aq XT'^qs aniijL "Sni 
-i[Bajq ja;jB sa;nniin s^T ^^R^ ^-lo™ -ion x ^Bq; ssa^ ;on ;sa; q;Snai;s ajisna; 
aq; nt najjojq sb aoaid ;sa; aq; no aq ^^Bqs ;as jo noi;Bnnnja;ap aqj, 

•adB; qo;aj;s aq; no pjooaj oi;Bnio;nB aq; niojj ;nao jad 
apqAi ;sajBan aq; 0; go pBaj noi;BSnoia aq; aABq'^^qs saoaid ;sa; Snijj 



pani] jsqqiu uo^^OQ 



-oijj JO aop^arauGiQQ 



Packing and other flat test pieces shall be tested exactly as prescribed for P""^ "J^ces*''" 
rubber hose, except that a clamp instead of a mandrel shall be used, and " ^ ^'°''^°' 
either the fabric or the rubber shall be fastened to the recording head accord- 
ing to the thickness of the rubber. 

If the rubber is not thicker than 14 inch, the fabric shall be fastened to 
the recording head. 

If the rubber is thicker than % inch, the rubber shall be fastened to 
the recording head. 

When fabric and fabric are to be separated, the heavier shall always be 
fastened to the power head. 

When heavy materials like belting are to be tested, the test pieces shall 
consist of not more than two plies of the fabric for any one test. 

The test pieces prepared and measured beforehand are placed in a hot Dry heat test. 
air oven at the specified temperature for the specified time, cooled to room 
temperature, and after resting 34 hours, the tensile strength and elongation 
tests made, compared with the untreated specimen, and the reduction cal- 
culated to the .nearest 0.1 per cent. 

The degree of hardness of a rubber compound shall be determined as Hardness test, 
follows : 

A smooth surface 1^ inch in diameter shall be prepared by buffing if 
necessary. The test piece shall be adjusted and clamped to a rigid base 
with the test area resting smoothly and firmly on the underlying support. 

The apparatus used shall be a standard asphalt penetrometer, preferably 
with electrical control. 

The hardness number shall be the distance in tenths of a millimeter that 
a No. 2 Roberts' sharp needle will penetrate the sample under a load of 200 
grams, acting for 5 seconds. 

Tube and cover test pieces for the gasoline test prepared, cut and meas- GasoUne test. 
ured as specified under the caption of Preparation of Tensile Strength Test 
Pieces shall be completely immersed in 57 to 63° Baume gasoline for a period 
of 48 hours at a temperature between 60° and 80° F. They shall then be 
removed, allowed to rest and freely evaporate in air at the same temperatxire 
for 24 hours. The tensile strength and elongation tests shall then be made, 
compared with the untreated specimens and the reductions caculated to the 
nearest 0.1%. 

Friction strength tests shall be made on one inch specimens cut for the 
mandrel test. After treatment with gasoline as above the friction strength 
shall be determined, compared with the untreated specimen, and the reduc- 
tions calculated to the nearest 0.1 per cent. 

The determination of steam resistance of hose shall be made by con- steamiest, 
necting 3-foot lengths to the steam supply pipe and maintaining the steam 
pressure required in the specifications, using a properly calibrated pressure 
gauge to maintain the proper pressure for the period or periods called for. 
After resting 24 hours the tensile strength, elongation and friction strength 
tests shall be made on the specimens cut, prepared and measured after the 
bteam test, compared with the untreated specimens and the reduction calculated 
to the nearest 0.1%. 



•9j[Bra piBpuB:js 1BV[%0 lo IqsoiQ jo aq n^'qs sdSnvS einssajd eqj^ 

•papiODSi aq ^^Bqs (qonr ai^nbs 
J9d amssaid spnnod m) sso^ ninniixBni aqjj -noi^^Bogioads :|tim aq; ui loj 
pa^^ra SB aq wxm. a^zzoti jo ja:;aniBip pn^ asoq jo azis jad a^Timra lad suo^^bS 
ni T[]Suai pajinbaj aij:} qSnoiq:^ gaiSiBqosip Aio^; jo ijnnouiB aqj, -apzon ladB:; 
;ioqs ^natn^jBdaQ aii^j Jjio^ ms^ pi'epuB^s b pnB asoq aq:j jo paa aSi^qastp 
dT{\ tiaaii^aq paqoB;:;^ aq n^^F aSn^S aitissaid laq^ouy -pa^sa; aq o:^ asoq aq:; 
JO giir[dnoo ;sig aq; poB ;nBipXq .10 ani( paaj aq; naaAi;aq paqoB;;B aq iiBxp 
aSn^S amssaid y -aoBjins an^^d b no ;q§tBi;s paqD;ai;s aq ^jBqs asoq aqj^ 

:SAi0Jpj SB 

apBui aq n^H^ ^BAia;BAi aq; jo ssaaq;ooTns aq; jo uot;Bainiia;ap aqj^ 

„ ^g asoq jaqqiu qont g puB %g 

„ 81 9^0'^ 3!-iq^J ^^^] 8 pn^ %8 

saqoui 5X 9Soq laqqni pnB otiqBj qom %x 

jpiT^f 0; aonB;si(i azis puB pnrv[ 



:Sjii.onoj SB pnij[ pnB azis 0; SnypjoooB aq ^Bqs J[ni5[ aq; 0; Sui^dnoo aq; jo 
aoatd ^tb; aq; inoij aonB;sip aq; ';sa; j[utj[ aq; loj noi;isod ;Bq; ui pana;sBj 
^tjaiTiDas puB jpip[ djBqs b q;m jps^t no ;Bp ;iiaq si asoq aq; naq^^^ 

•50 ;ioqs pajfniif naqji puB 
sntpBi saqoui ^g jo apiio b ui paAJiio naqm ';qgiBi;s ;no piBj uaqAV ajnssaid 
Sui;siuq 0; pa;Dafqns aq {jBqs asoq 'suoi;Bogioads aq; ui joj'pajiBO uaq^ 

•pa4i0{|0j aq n^qs uoi;BogiDads ;iun aq; ni pa;B;s sb ajnpaooid aq; asBO 
qatq^si ui 'apBin Sutaq aiB s;uainajnsBain anq^i ainssaid ppq 0; aiui; jo poiiad 
aq; puB najjB; aq 0; ajB s;naraaJTisBaui qoiqji ;b ainssaid aq; o; piBgai ui 
ainpaooid SoioSaioj aq; jCjipora sanii;auios Xbiu noi;BDgpads ;iim aqj, 

•sa;nuini g uBq; aiora ;oa ;naniaiTisBain loj p[aq aq j^Bqs ;sa; lapun 
asoq aq; puB a;tiuiin lad spunod OOI P ^l^^i 9^^ ^^ apBca aq n^qs ainssaid ui 
asBaioui aqj, -aSnBS pazipiBpnB;s b q;im painsBam aq jjBqs s;sa; ainssaij 

■spnnod oi ^^ ^^^^ 
-said aq; q;m ;uauiainsBaui jBUigiio Snp[B; £q uiSaq uaq; ^jBqs ;sa; aqj, 

•paqddB qoni aiBnbs lad spunod oi Jo ainssaid 
■B puB pasop aq uaq; n^^js j[doo iib aqj, -adBosa 0; iib aq; aoijb 0; uado jjood 
iiB aq; SuiABa^ 'ia;BAv q;iAi pa[jg puB dumd 10 aui^ aa;BM aq; o; pa;Daiinoo 
anij ;qStBi;s b ni aoBjins auBjd b uo ;no paqo:;ai;s aq wbx{9 asoq aqj^ 

riauuBui Snmonoj 
aq; ui apBur aq jjBqs ainssaid jooid 10 Sui;sinq jo uoi;Bniniia;ap aqj, 

•snoiod paiapisuoo aq ^Bqs asoq aq; 's[jbai aq; jo am; 
-oni;s aq; ui paugnoD iib aq; 0; anp ;ou si qoiqa iib jo adBosa ;oni;sip b si 
aiaq; jj •ia;BA ui paSiainqns aq ^Bqs 'ainssaid lapun {ji;s 'q;Suaj aq; poiiad 
siq; JO pna aq; ;y •sa;nuini g loj pauiBjuiBui aq {^qs ainssaid aqjL ■;aaj 
g ;sBa^ ;b ioj asoq aq; q;m asmq;Sua{ ;no aq uaq; ^^Bqs laAOO aqx 'ains 
-said IIB spunod o^T 0; pa;oa.Cqns aq jjBqs ;sa; 10 j pa;Daps q;Snaj aqx 



•Bjnesajd 
joojd JO 3ai}amq 
}0 noijoaroilajoa 



CHEMICAL 

GENEEAL. 

Samples shall be taken representative of the lots to be tested. Samples. 

Blanks shall be run and deductions made according to the lots of Blanks 
reagents. 

In the event of any determination not falling within the limits given in checks. 
the specification, a check test shall be made before the report is sent out. 

Prepare a sample of not less than 15 grams, taking pieces from various Preparation of i 
parts of the original sample. The backing of fire hose shall be buffed ofE ™ "' 
before grinding. In all other hose separate samples of tube and cover shall 
be made, without removing the backing or friction compound. Other rubber 
goods built up with friction fabric shall have the rubber layers ground up 
without removal of the adhering friction compound. 

The sample shall be cut into small pieces and then run through the Grinding, 
grinder, until all will pass a standard 20-mesh sieve. Care must be taken 
to see that the grinder does not become appreciably warm during the grinding. 
If the natiire of the material is such that it gums together so that it will not 
pass through the sieve, as would be the case with undervulcanized samples, it 
will be sufficient to pass the material through the grinder twice and accept all 
the material for the final sample. Crude rubber shall be cut with scissors. 

Pass a strong magnet through the sample to remove any metal from the 
grinders, mix thoroughly, and put in tightly stoppered bottles. Do not 
expose to sunlight or heat. 

Samples of hard rubber shall be prepared for analysis by rasping. Hard rubber 

EEAGENTS. 

Acetone shall be distilled not more than 10 days before use over anhydrous 
potassium carbonate, using the fraction 56° to 57° C. 

Alcoholic potash shall be of normal strength, made by dissolving the 
required amount of potassium hydroxide in absolute alcohol the day before 
use, and allowing to settle. Only the clear solution shall be used. 

Barium chloride solution shall be made by dissolving 100 grams of 
barium chloride in 1 liter of distilled water, and adding 2 or 3 drops of 
concentrated hydrochloric acid. If there is any insoluble mater or cloudiness, 
the solution shall be heated on the steam bath overnight, and filtered. 

Refined naphtha shall be prepared by shaking out the fraction boiling 
below 80° C. with concentrated sulphuric acid until the acid is only slightly 
colored, washing with sodium carbonate solution and water and redistilling. 

All reagents shall be of C. P. quality. 



•piOB DuopjDOipjfq p8:)n[Tp q:;ui 
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■s^oii/VHiHaaxaa 



■»!>BJ}X8 ono}sov 



Extract a 5 gram sample exactly as under "acetone extract" after placing waxy Hydrocarbon 
0.5 gram of finely powdered pure copper in the bottom of the extraction tube. 
Evaporate the acetone and dry the tube at 95° to 100° C. until the odor of 
acetone has disappeared. Add 25 c. c. of refined naphtha, warm and filter 
into a separatory funnel. Eepeat the operation with naphtha at least twice 
and wash the paper with a small quantity of refined naphtha. Shake out with 
10 c. c. portions of concentrated sulphuric acid until the acid is no longer 
or only slightly colored, draining off all viscous material, shake the imited 
acid washings with 25 c. c. of refined naphtha, drain off and reject the clear 
acid portion, shake out the remainder with 25 c. c. of distilled water to break 
any emulsion and transfer the naphtha to the main volume. Shake out once 
with 25 c. c. of distilled water, once with 25 c. c. of a 5 per cent sodium car- 
bonate solution, and finally at least four times with distilled water or vmtil 
the washings are neutral. Transfer the naphtha solution to a weighed Erlen- 
meyer flask, distill off the naphtha, add a small amount of alcohol to the 
residue and evaporate rapidly in a slanting position to remove water from 
the wax. Dry at 105° to 110° C. in one hour periods to constant weight, 
desiccate till cool and weigh. Calculate and record as "waxy hydrocarbons." 

Extract a one gram sample as under acetone extract for 4 or more hours. Mineral FUiers. 
and dry the rubber at 95° to 100° C. until the odor of acetone has disappeared. 
Transfer to a weighed centrifuge tube, add 50 c. c. of aniline and 10 c. c. of 
nitrobenzol. Digest for 20 hours at 150° to 160° C. with occasional stirring 
until solution is complete. Cool, fill the tube with ether and centrifuge. 
Wash and centrifuge at least four times with ether, stirring the pigment up 
thoroughly each time. Dry the tube to constant weight at 100° to 106° C. 
Cool in a desiccator and weigh. Unite the decantates, distill off the ether, 
transfer the residue with the aid of benzol to a weighed porcelain or silica 
dish, bum off the organic matter, cool in a desiccator and weigh. Add the 
weights of material found in the tube and dish, calculate and record as "min- 
eral fillers." 

One gram of finely ground rubber sample is placed in a weighed porcelain (^*"e™|)°' 
crucible. 

The crucible is covered, placed upon an asbestos pad and heated at a low 
temperature to drive off organic matter. The lid of the crucible is removed 
and the edges of the crucible heated to burn off organic matter. The ash is 
inspected for any unburned charred matter and, if necessary, is reheated. 

The crucible is weighed after cooling and the percentage of ash calculated 
as usual. 

No correction is made for sulphur in the ash. 

Mix a 0.5-gram sample with 6 grams of potassium carbonate and 4 grams Total sulphur. 
of sodium peroxide in a dry 60 c. c. iron crucible. Fuse by heating the 
surface of the mixture a few seconds with a burner. Cover and heat to quiet 
fusion for 15 to 20 minutes. Eotate the crucible while the melt solidifies. 
Cool, place in a casserole containing 200 c. c. of distilled water, and heat 
gently until dissolved, lifting and rotating the crucible to accelerate solution. 
Add a few drops of alcohol to reduce and precipitate the manganese derived 
from the iron, filter, wash well with hot water, acidify the filtrate with hydro- 
chloric acid, using Congo paper as an indicator, dilute to 400 c. c. volume, 
heat to boiling and precipitate with 10 c. c. of a 10 per cent barium chloride 
solution. Allow to stand over night, filter on ashless paper, wash ten times 
vidth hot water, transfer to a small weighed porcelain crucible, char the paper, 
ignite, cool in a desiccator and weigh. CalciUate and record as "Total Sulphur 
in All Forms," using the factor 0.1374. 



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•;q'SiaAi sthbiS g nBq; ssa^ ;on sdij;s lo du;s b no not;Bniniia;ap aq; q^tsji 



JO noT^Buiuija^aQ 



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